Beamwidth Research Articles

Fundamental precision limits of fluorescence microscopy: a perspective on MINFLUX.

Over the past years, fluorescence microscopy (FM) has steadily progressed in increasing the localization precision of fluorescent emitters in biological samples and led to new claims, whose rigorous validation remains an outstanding problem. We present a novel, to the best of our knowledge, multi-parameter estimation framework that captures the full complexity of a single-emitter FM localization experiment. We showcase our method with Minimum Flux (MINFLUX) microscopy, among the highest-resolution approaches, demonstrating that (i) the localization precision can be increased only by turning the illumination intensity up, thus increasing the risk of photo-bleaching, and it is independent from the beams' separation, and (ii) in presence of background noise, the localization precision decreases with the beams' separation. Finally, we apply our method to Minimum Flux Stimulated Emission Depletion (MINSTED) microscopy, showing that a reduction of the beam width can provide similar performance to MINFLUX.

Study of effect of nanomaterial above the add layer on performance parameters of plasmonic structure

In this paper, we explored the effect of adding a nanomaterial layer above the add layer on performance parameter of the considered plasmonic structures (conventional, four and five layer SPR sensors). These structures are stimulated by the COMSOL Multiphysics. We have considered LiNbO3 as an add layer over a thin film of gold. Further, Graphene, Black Phosphorene, Mxene, MoS2 MoSe2, WS2 and WSe2 as nanomaterial are considered over add-layer. First, we optimised the thickness gold and LiNbO3. After that, we calculated reflectance and magnetic field dependent performance parameters, i.e., shift in resonance angle (∆θr), full beam width (FBW), sensitivity (S), detection accuracy (DA), quality factor (Q. F.), figure of merit (FoM), field intensity at different interfaces (metal-sensing medium (M-S), metal-dielectric (M-D), dielectric-sensing medium (D-S), dielectric-nanomaterial (D-N), nanomaterial-sensing medium (N-S), and penetration depth (PD) for the considered plasmonic structures. The minimum ∆θr is obtained for conventional structure i.e. 1.492° and maximum ∆θr is obtained for WS2 as nanomaterial used in five layer SPR sensor i.e., 2.052°. Moreover, FBW is also maximum for five layer SPR sensor with WS2 as nanomaterial i.e., 6.8430°. Moreover, PD has maximum value for conventional SPR sensor i.e., 190.894 nm, 175.94 nm for four layer SPR sensor and less than 175.94 nm for five layer SPR sensor. This comparative study will help to choose add-layer with nanomaterial over add layer and metal thin film layer in a SPR sensor for the detection of analyte or molecules present in the sensing medium.

Increasing the Beam Width and Intensity with Refraction Power Effect Using a Combination of Beam Mirrors and Concave Mirrors for Surgical-Fluorescence-Emission-Guided Cancer Monitoring Method.

The primary goal during cancer removal surgery is to completely excise the malignant tumor. Because the color of the tumor and surrounding tissues is very similar, it is difficult to observe with the naked eye, posing a risk of damaging surrounding blood vessels during the tumor removal process. Therefore, fluorescence emission is induced using a fluorescent contrast agent, and color classification is monitored through camera imaging. LEDs must be irradiated to generate the fluorescent emission electromotive force. However, the power and beam width of the LED are insufficient to generate this force effectively, so the beam width and intensity must be increased to irradiate the entire lesion. Additionally, there should be no shaded areas in the beam irradiation range. This paper proposes a method to enhance the beam width and intensity while eliminating shadow areas. A total reflection beam mirror was used to increase beam width and intensity. However, when the beam width increased, a shadow area appeared at the edge, limiting irradiation of the entire lesion. To compensate for this shadow area, a concave lens was combined with the beam mirror, resulting in an increase in beam width and intensity by more than 1.42 times and 18.6 times, respectively. Consequently, the beam width reached 111.8°, and the beam power was 13.6 mW. The proposed method is expected to be useful for observing tumors through the induction of fluorescence emission during cancer removal surgery or for pathological examination in the pathology department.

Energy dependence of x‐ray beam size produced by polycapillary x‐ray optics

AbstractIn this work, we studied the x‐ray energy dependence of x‐ray beam diameter focused by polycapillary optics. A quantitative beam diameter–energy relation enables more accurate estimation of the element‐specific interrogation area of a sample using the compositional maps produced by a micro‐XRF system. This improves upon our ability to visualize individual beam‐diameter sized mineral grains and in turn directly benefits Planetary Instrument for X‐ray Lithochemistry (PIXL) analyses of martian soil in addition to benefitting other micro‐focused x‐ray fluorescence (XRF) systems. The spatial distribution of an array of characteristic XRF emission lines was measured by sampling via a knife‐edge approach with small motor stepping of the beam across target edges. Data taken as part of this effort, from the Planetary Flight Model (PFM), were limited to only seven beam energies corresponding to the elements Ni, Cu, Se, Ta, Au, Ti and Ba. Hence, we conducted additional analysis using JPL's lab‐based breadboard (LBB) micro‐XRF system, a system that emulates PIXL's functionality where we measured beam diameter corresponding to 18 elements: Na, Mg, Al, Si, Cl, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Ge, Se, Sr and Mo. The experimental results were also compared with Monte Carlo simulations. The beam diameter (y)–energy (x) relation that we obtained for LBB was y = 185.79 exp(−0.078x) whose exponential component was then used to get a more accurate relation for the PFM even with the limited data set: y = 227.53 exp(−0.078x). The difference in the two coefficients for the PFM and LBB stems mainly from the difference in the polycapillary optic design, and this work establishes x‐ray beam diameter versus energy relation quantitatively for both the systems.

Wideband circularly polarized reconfigurable metasurface antenna for 5G applications

Abstract A framework of a metasurface (MTS) – based wideband circularly polarized (CP) reconfigurable antenna for fifth generation (5G) wireless systems operating in the sub-6 GHz mid-frequency range is presented in this article. The proposed structure contains a simple patch antenna, which serves as the primary source, a shorting pin, two ring slots, and a metasurface superstrate. The shorting pin and two ring slots produce perturbation resulting in circular polarization with a narrow axial ratio (AR) bandwidth. A metasurface (MTS) superstrate composed of 4 × 4 rectangular patches stacked over the primary source antenna generates additional resonances that significantly improve the −10 dB impedance and 3 dB axial ratio (AR) bandwidth. Two PIN diodes are employed to alter the circular polarization between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The prototype is made using an FR-4 epoxy substrate and has an overall size of 50 mm × 35 mm × 4.2 mm. The antenna has a −10 dB bandwidth of 44 % (4.0–6.2) and a 3 dB axial ratio bandwidth of 28 % (4.2–5.6). It also has a 3 dB beam width of 74° and 85° in the E and H planes, a gain of 7.1 dBi, cross-polar isolation of more than 15 dB, and a unidirectional radiation pattern. The simulated and measured results confirm that the implemented antenna is promising for sub-6 GHz 5G communication systems, particularly cognitive radio, wireless body area networks (WBAN), and satellite communication systems.

Vortex inverted pin beams: mitigation of scintillations in strong atmospheric turbulence.

We recently introduced a new class of optical beams with a Bessel-like transverse profile and increasing beam width during propagation, akin to an "inverted pin." Owing to their specially engineered distribution, these beams have shown remarkable performance in atmospheric turbulence. Specifically, inverted pin beams (PBs) were found to have a reduced scintillation index as compared to collimated or focused Gaussian beams as well as other types of pin beams especially in moderate to strong turbulence. In this work, we demonstrate that inverted pin beams carrying orbital angular momentum (OAM) can further suppress intensity scintillations in moderate to strong irradiance fluctuation conditions. Our results can be useful in improving the performance and link availability of free-space optical communication systems.

A Corrugated Edged Tapered Slot Antenna with Low Cross-Polarization and Moderate Gain for Phased Array Systems

ABSTRACT This paper presents a miniaturized Vivaldi antenna with a scan volume of ± 30° designed for the 6–18 GHz tactical operational band, commonly employed in phased array systems and modern surveillance applications. The proposed antenna offers enhanced radiation characteristics, low cross polarization, broad beam width, and moderate gain. The design presented in this paper follows a step-by-step approach to achieve enhanced performance in terms of multi-octave bandwidth and compact size. Initially, a traditional Vivaldi antenna was designed and examined, with a modified feed structure. Subsequently, corrugated edges were inserted into the antenna, increasing its electrical length and resulting in good impedance matching, especially in the 6–10 GHz frequency band. A prototype model is fabricated and tested to validate its performance against the simulation results. The measured results demonstrate that the return loss (S11) remains below −10 dB across the operating frequency range, achieving a 50% bandwidth, with a gain of 3–7 dB, and improved co-cross polarization of −23 dB at 6 GHz and −26 dB at 18 GHz.

Effect of steady-state thermal blooming on partially coherent radially polarized beams propagating in the atmosphere

We undertake a computational study of the steady-state thermal blooming effect on a special class of partially coherent vector beams, called partially coherent radially polarized (PCRP) beams, propagating through the atmosphere. A computational propagation model that is based on a multi-phase screen method is established to simulate partially coherent vector beams. With the use of this model, the propagation properties of PCRP beams with different initial powers and spatial coherence widths are studied in detail, including average intensity distribution, r.m.s. beam width, and polarization. Our results unveil that PCRP beams can effectively reduce or overcome the negative effects caused by thermal blooming when the initial coherence width falls below a certain threshold. Further, it is shown that the spatial distribution of degree of polarization (DOP) is significantly affected by the thermal blooming during beam propagation, whereas the global DOP (integrating the DOP over a beam’s cross-section) is not.

A 77 GHz Transmit Array for In-Package Automotive Radar Applications

A packaged transmit array (TA) antenna is designed for automotive radar applications operating at 77 GHz. The compact dimensions of the proposed configuration make it compatible with standard quad flat no-lead package (QFN) technology. The TA placed inside the package cover is used to focus the field radiated by a feed placed in the same package. The unit cell of the array is composed of two pairs of stacked patches separated by a central ground plane. A planar patch antenna surrounded by a mushroom-type EBG (Electromagnetic Band Gap) structure is used as the primary feed. An analytical approach is employed to evaluate the primary parameters of the suggested TA, including its directivity, gain and spillover efficiency. The final design has been refined using comprehensive full-wave simulations. The simulated gain is 14.2 dBi at 77 GHz, with a half-power beamwidth of 22°. This proposed setup is a strong contender for highly integrated mid-gain applications in the automotive sector.

Wide cone beam CT dosimetry: Analysis of results and uncertainty evaluation

ObjectiveTo investigate the consistency of the recommended methodology, we analyzed the dosimetric results obtained for each setup beam shaping filter and tube voltage and evaluated the uncertainty associated with the full dose measurement process. MethodsA 300-mm PTIC was used to validate the results obtained with the 100-mm PTIC. Considering the other dosimetric parts, a cylindrical 160-mm diameter PMMA phantom and a cylindrical 320-mm diameter PMMA phantom were also used in the experimental protocol. ResultsFor the lowest and highest tube voltages available, the CTDIair,160 values obtained by 1-step dosimetry with the 300-mm PTIC were greater than the respective values obtained by 2- and 3-step dosimetry with the 100-mm PTIC. ConclusionThis study established that careful positioning of the 100-mm PTIC in 2 or 3 steps, as well as proper execution of the other dosimetric parts recommended by the IAEA, represents a validated approach within up to 20% uncertainty for wide cone beam CT dosimetry.

Repairing weld for directly solidified Ni-based superalloy substrates using directed energy deposition of Inconel 625

Although the maintenance, repair, and operation of gas turbine systems are important issues in enhancing the operation of power units, advanced welding repair processes have limitations in depositing directionally solidified Ni-based superalloy components. To overcome this problem, in this study, a directed energy deposition method was applied to repair directionally solidified components using an Inconel 625 alloy. The rapid cooling rate and small laser beam diameter during directed energy deposition minimized the heat-affected zone and duration in the mushy zone, resulting in crack inhibition at the interface. The first laser scan partially melted the substrate and formed a mixing zone with a chemical composition gradient. By combining the chemical compositional gradient and dislocation accumulation due to repetitive solidification, that is, with the melting cycles of directed energy deposition, the thermal stability decreased, resulting in recrystallization and grain growth in the mixing zone. Consequently, the crack-free continuous interface of the partially repaired components did not induce tensile fracture near the interface. Although the mechanical properties of the IN625 deposit layer were degraded by severe heat treatment of the substrate, the results demonstrated that energy deposition with post-heat treatment is an effective approach in repairing Ni-based superalloy components without cracks and inclusion initiation.

Modeling of High-Power Graded-Index Fiber Amplifiers

Graded-index fibers have been used in recent years to make high-power fiber lasers and amplifiers. Such fibers exhibit self-imaging, a phenomenon in which any optical beam periodically reproduces its original shape in undoped fibers (no gain). In this work, we employed analytic and numerical techniques to study how self-imaging affects the evolution of a signal beam inside a nonlinear graded-index fiber amplifier, doped with a rare-earth element and pumped optically to provide gain all along its length. We also exploited the variational technique to reduce the computing time and to provide physical insights into the amplification process. We compared the variational and fully numerical results for the two pumping schemes (clad pumping and edge pumping) commonly used for high-power fiber amplifiers and show that the variational results are reliable in most cases of practical interest. The stability of the signal beam undergoing amplification is examined numerically by launching a noisy Gaussian beam at the input end of the amplifier. Our results show that the quality of the amplified beam should improve in the case of edge pumping when a narrower pump beam provides an optical gain that varies considerably in the radial direction of the fiber. Such an improvement does not occur for the clad pumping scheme, for which the use of a relatively wide pump beam results in a nearly uniform gain all along the fiber.

Branched flow of light and interplay with input phase front curvature in a disordered photonic lattice

Branched flow refers to the bifurcation of waves as they propagate through customized disordered media, leading to the creation of multiple channels or branches. This dynamic wave phenomenon has been observed in various disordered systems under specific conditions. In our study, we demonstrate the branched flow of light within a disordered photonic lattice and establish that the intensity distribution of these branches follows Lévy statistics. This behavior is more pronounced when the wavefront of the input light beam is adjusted, resulting in the propagation of more stable branches through the structure. We also investigated the formation of light branches with varying input beam widths and the impact of two simultaneous input beams on the disordered photonic lattice. Our findings indicate that the distribution of branches in the disordered system can be controlled by shaping the wavefront of the input beam, which has potential applications in imaging, nano-lasing, and integrated photonic components. This research opens new avenues for fundamental studies on the manipulation of light through complex photonic systems.

Equation for the simplified calculation of the horizontal shear stress in composite beams of rectangular cross-section with considerable width

The theory of elasticity allows describing the law of variation of shear stresses Τzy and Tzx for a beam of rectangular cross-section, however, the expressions are extensive and complex. For beams with a width/depth ratio equal to 0.25, it is allowed to calculate approximately the maximum shear stress Tzy, with the Collignon-Zhuravski equation. Depending on the width/depth ratio of the beam, it will depend on the percentage of error made. Unfortunately, for the shear stress Tzx there is no approximate formula available to determine the value of the shear stress. Using a simplified procedure, a differential beam element was analyzed in the elastic field for different width/depth ratios and a very simple expression was obtained. The results of the approximate formula were compared with the values obtained from the application of the exact formula and the results of a linear numerical analysis using the finite element method. For cross-sections of homogeneous beams and composite beams of considerable width, it is essential to determine the horizontal shear stresses Tzx in particular in the case of vertical planks, arranged side by side, connected solidly by horizontally arranged mechanical connectors, since the shear stresses Tzx developed across the width of the cross-section may considerably exceed the vertical shear stresses Tzy and furthermore govern the pattern, spacing and cross-section of the mechanical connectors. The validity of the approximate expression for calculating the maximum value of the shear stress Tzx was limited to beams with a width/depth ratio between 0.25 and 10.0.

Interference of high-order perfect optical vortex beams

We investigate the interference of high-order perfect optical vortex (POV) beams with different topological charges. Through numerical simulations, we reveal a remarkable phenomenon: keeping the beam width, and beam radius fixed while changing the topological charge, the splitting of the composite POV beam into two distinct individual perfect vortices occurs exactly at the same inter-axial separation. The observed interference pattern exhibits pronounced sensitivity to factors such as axial separation, phase shift, beam radius, and topological charges of the constituent beams. Notably, our findings are contrasted with the interference of high-order Laguerre-Gauss (LG) beams, highlighting that the splitting of composite vortices into their individual components is more rapid in the case of LG beams. We also investigate the evolution of the interference pattern for both POV, and LG beams along the propagation direction in free-space. Our research provides significant insights into the distinct interference properties of high-order POV beams, presenting potential applications in the fields of optical manipulation and communication systems.

Wideband Circularly Polarized Dielectric Resonator Antenna With Wide Overlapped Axial-Ratio and Half-Power Beamwidths

Wideband Circularly Polarized Dielectric Resonator Antenna With Wide Overlapped Axial-Ratio and Half-Power Beamwidths

Low-profile, low sidelobe array antenna with ultrawide beam coverage for UAV communication

This paper presents a design method to implement an antenna array characterized by ultra-wide beam coverage, low profile, and low Sidelobe Level (SLL) for the application of Unmanned Aerial Vehicle (UAV) air-to-ground communication. The array consists of ten broadside-radiating, ultrawide-beamwidth elements that are cascaded by a central-symmetry series-fed network with tapered currents following Dolph-Chebyshev distribution to provide low SLL. First, an innovative design of end-fire Huygens source antenna that is compatible with metal ground is presented. A low-profile, half-mode Microstrip Patch Antenna (MPA) is utilized to serve as the magnetic dipole and a monopole is utilized to serves as the electric dipole, constructing the compact, end-fire, grounded Huygens source antenna. Then, two opposite-oriented end-fire Huygens source antennas are seamlessly integrated into a single antenna element in the form of monopole-loaded MPA to accomplish the ultrawide, broadside-radiating beam. Particular consideration has been applied into the design of series-fed network as well as antenna element to compensate the adverse coupling effects between elements on the radiation performance. Experiment indicates an ultrawide Half-Power Beamwidth (HPBW) of 161° and a low SLL of −25 dB with a high gain of 12 dBi under a single-layer configuration. The concurrent ultrawide beamwidth and low SLL make it particularly attractive for applications of UAV air-to-ground communication.

Laser-induced ultrasound in multiple thin layers-An analytical solution.

Laser-induced ultrasound is based on the thermo-elastic conversion of absorbed short light pulses to pressure pulses. In the work presented here, laser-induced ultrasound in a planar structure of interconnected layers with variations in optical, thermal, and mechanical properties is studied. Layered structures can be used for generating wideband ultrasonic pulses specific to a chosen application. An analytical time-domain solution is derived for the resulting pressure transmitted from the layered structure. The solution is derived for an arbitrary number of layers with an arbitrary optical absorption profile. Free space Green's functions with image sources are used to derive the solution. A solution employing the Beer-Lambert law is also proposed. The simplification with reflections only at the boundaries is in agreement with previous published results. The spectral properties of the generated pulse are derived, where the effects of optical absorption coefficients and layer thicknesses are shown. The analytical solution is compared to one-dimensional (1D) simulations and a three-dimensional (3D) simulation, realised as a two-dimensional (2D) axially symmetric case, using the matlab toolbox k-Wave. The 3D simulation on-axis pressure agrees well with the 1D analytical solution when the diameter of the laser beam is larger by approximately 1 order of magnitude than the thickness of the planar layered structure.

High voltage determination and stabilization for collinear laser spectroscopy applications.

Fast beam collinear laser spectroscopy is the established method to investigate nuclear ground state properties such as the spin, the electromagnetic moments, and the charge radius of exotic nuclei. These are extracted with high precision from atomic observables, i.e., the hyperfine splitting and the isotope shift, which become possible due to a large reduction of the Doppler broadening by compressing the velocity width of the ion beam through electrostatic acceleration. With the advancement of experimental methods and applied devices, e.g., to measure and stabilize the laser frequency, the acceleration potential became the dominant systematic uncertainty contribution. To overcome this, we present a custom-built high-voltage divider, which was developed and tested at the German metrology institute, and a feedback loop that enabled collinear laser spectroscopy to be performed at a 100-kHz level. Furthermore, we describe the impact of field penetration into the laser-ion interaction region. This affects the determined isotope shifts and hyperfine splittings if Doppler tuning is applied, i.e., the ion beam energy is altered instead of scanning the laser frequency. Using different laser frequencies that were referenced to a frequency comb, the field penetration was extracted laser spectroscopically. This allowed us to define an effective scanning potential to still apply the faster and easier Doppler tuning without introducing systematic deviations.

High-Gain Patch Antenna with Stacked Director Patches Using an End-Fire Theory for Microwave Power Transfer Applications

This paper proposes a high-gain patch antenna with stacked director patches. The proposed antenna is composed of a driven patch and seven stacked director patches, which enable it to achieve high gain. The driven patch is printed on a TLY-5 substrate, and the director patches are stacked in seven layers on top of the driven patch. The proposed antenna has a reflection coefficient of −21.7 dB at 5.8 GHz. The bore-sight gain of the proposed antenna is improved by 6.65 dB on average over the frequency range from 5.4 GHz to 6.2 GHz compared to a driven patch without director patches. At 5.8 GHz, the measured bore-sight gain is 12.5 dBi, which is a 5.5 dB increase compared to a driven patch without director patches. The measured half-power beamwidths are 48° and 42° in the zx- and zy-planes, respectively.